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Tech Beat - October 26, 2010

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Editor: Michael Baum
Date created: October 26, 2010
Date Modified: October 26, 2010 
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NIST Ships First Programmable AC/DC 10-Volt Standard

Extending its 26-year tradition of innovative quantum voltage standards, researchers at the National Institute of Standards and Technology (NIST) have begun shipping a new 10-volt standard to users around the world. The programmable system measures both direct current (DC) and alternating current (AC) voltages.

NIST AC/DC 10-volt standard chip.

Integrated circuit for NIST's new programmable AC/DC 10-volt standard. The chip contains about 300,000 superconducting Josephson junctions (located along horizontal lines at right-center of micrograph).

Credit: NIST
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The new 10-volt system* builds on a number of previous NIST inventions, from the initial 1-volt standard in 1984 through the 2006 unveiling of the world’s first precision instrument for directly measuring AC voltages.** Because the measurements are made using integrated circuits based on quantum phenomena and simple equations that can be reproduced reliably, NIST quantum voltage standards represent a major advance over historical artifact standards, which were essentially chemical batteries that were influenced by environmental conditions and sometimes drifted over time.

About 50 standards labs, military organizations, and private companies worldwide calibrate voltmeters using standards based on earlier generations of NIST-developed technology. Products made with these instruments range from compact disc players to missile guidance systems.

The new technology relies on superconducting integrated circuits containing about 300,000 Josephson junctions, whose quantum behavior ensures that every junction produces exactly the same voltage. Quantum voltage standards are based on the Josephson effect, observed when two superconducting materials are separated by a thin insulating or resistive film and a current tunnels through the barrier (or junction). When microwave radiation of a known frequency is applied, the junction generates a voltage that can be calculated based on that frequency and two fundamental constants of nature.

The new standard offers unique advantages over previous generations. For DC metrology, benefits include higher immunity to noise (interference), output stability, and ease of system setup and operation. The system also enables a wider range of applications by producing AC waveforms for accurately calibrating AC signals with frequencies up to a few hundred hertz. A key advance is the use of junctions with metal-silicide barriers that produce stable steps and have uniform electrical properties. The system also incorporates new electronics, automation software, and measurement techniques.

The first system was shipped to the Kennedy Space Center in Florida earlier this month, and others are on order by standards laboratories in Brazil and Taiwan.

* C.J. Burroughs, P.D. Dresselhaus, A. RÜfenacht, D. Olaya, M.M. Elsbury, Y. Tang and S.P. Benz. “NIST 10 V programmable Josephson Voltage Standard System.” Presented at the Conference on Precision Electromagnetic Measurements, Daejon, Korea, June 14, 2010.
** See NIST newsletter article “Road to AC Voltage Standard Leads to Important Junction” at www.nist.gov/pml/road_062006.cfm.

Media Contact: Laura Ost, laura.ost@nist.gov, (303) 497-4880

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NIST Microrobotics Challenge Seeks Miniature Medics and Maze Masters

They’ve played soccer, run dashes and deftly inserted pegs into holes—all within a world that can fit inside a single grain of rice. Now, it’s time for microrobots—mechanical workhorses whose dimensions are measured in micrometers (millionths of a meter)—to show off their abilities in a friendly competition of miniature maneuvering and manufacturing skills.

The National Institute of Standards and Technology (NIST), in collaboration with IEEE, is inviting teams currently engaged in microrobotic, microelectronic or microelectromechanical systems (MEMS) research to participate in the NIST Mobile Microrobotics Challenge 2011. The competition will be held as part of the IEEE International Conference on Robotics and Automation, May 9-13, 2011, in Shanghai, China.

Viewed under a microscope, the microbots are operated by remote control and move in response to changing magnetic fields or electrical signals transmitted to a microchip operating environment. The microbots are a few tens of micrometers to a few hundred micrometers long, and their masses can range from less than a milligram down to just a few nanograms (billionths of a gram). They are manufactured from materials such as aluminum, nickel, gold, silicon and chromium.

The Mobile Microrobotics Challenge 2011 will pit tiny robotic contestants against each other in two events: a mobility challenge in which microrobots will be required to navigate a planar (two-dimensional) maze having the diameter of a pin head; and a microassembly challenge where the competitors must put together multiple microscale components in a narrow channel to simulate operations within a blood vessel by a future medical applications microbot.

These events are designed to “road test” agility, maneuverability, response to computer control and the ability to move objects—all skills that future industrial microbots will need for tasks such as microsurgery within the human body or the manufacture of microscopic electronic devices.

NIST is organizing the 2011Mobile Microrobotics Challenge with the IEEE Robotics and Automation Society. NIST’s goal in coordinating competitions between the world’s smallest robots is to show the feasibility and accessibility of technologies for fabricating MEMS, which are tiny mechanical devices built onto semiconductor chips. The contests also drive innovation in this new field of robotics by inspiring young scientists and engineers to become involved.

To apply for the NIST Mobile Microrobotics Challenge, teams must submit a proposal by Dec. 1, 2010, by electronic mail to microrobotics2011@nist.gov, or by standard mail to: NIST Microrobotics Challenge 2011, c/o Craig McGray, NIST, 100 Bureau Dr., MS 8120, Gaithersburg, MD 20899-8120. Proposals must include: a roster of individuals contributing to the team; contact information for the team leader; a list of the facilities available for fabrication, operation and characterization of microrobots; an overview of the microrobot design; an overview of the intended capabilities of the microrobot; and an overview of the fabrication process to be used.

Official rules for the NIST Mobile Microrobotics Challenge 2011 may be found at www.nist.gov/pml/semiconductor/mmc/.

Media Contact: Michael E. Newman, michael.newman@nist.gov, (301) 975-3025

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'Sí' on the New SI: NIST Backs Proposal for a Revamped System of Measurement Units

Taking the first steps of what would be a major historical advance in the science of measurement, the National Institute of Standards and Technology (NIST) is participating in a worldwide effort to recommend major revisions to the International System of Units (SI), the modern metric system that is the basis of global measurements in commerce, science and other aspects of everyday life. The new SI, which would be based on seven constants of nature, would enable researchers around the world to express the results of measurements at new levels of consistency and accuracy.

NIST watt balance experiment.

In support of a proposal to revise the International System of Units (SI) so that it would be based on constants of nature, NIST efforts such as the watt balance experiment (pictured) offer new ways of determining an accurate value of the Planck constant h, thereby contributing to a definition of the kilogram based on physical constants.

Credit: Steiner/NIST
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The most significant change in the possible future revision of the SI would be in the kilogram, the only one of the SI’s seven base units* still defined in terms of a material “artifact”: a 130-year-old platinum-iridium cylinder maintained at the International Bureau of Weights and Measures in France. The kilogram artifact poses long-term problems because its mass changes slightly over time. The proposed revision “puts the SI on a firm foundation,” says Ambler Thompson, a NIST scientist involved in the international effort. “We get rid of the last artifact.”

In the current SI, it’s not just the unit of mass that depends on the kilogram. The definitions of the ampere (electric current), mole (amount of substance) and candela (luminous intensity) ultimately depend on the platinum-iridium artifact. For example, a mole is currently defined as the number of carbon-12 atoms whose total mass is 12 grams.

The new proposal defines the kilogram in terms of the Planck constant h**, an important constant in quantum physics, which is expressed in units containing the kilogram. Efforts at NIST such as the watt balance experiment and determinations of the mass of one mole of silicon atoms offer new ways of determining an accurate value of h, thereby contributing to a more reliable definition of the kilogram.

The new SI would specify agreed-upon values of the seven constants, according to the results of an analysis published by CODATA (Committee on Data for Science and Technology)of all of the relevant data. Fixed values of constants would then define all base units. For example, the ampere would be formally defined in terms of the electric charge of a proton, the kelvin (temperature) in terms of the Boltzmann constant***, and the mole in terms of the Avogadro constant. However, before the revised SI could be implemented, additional experiments are needed to obtain more accurate values for some of the constants, especially the Planck, Avogadro, and Boltzmann constants.

The Consultative Committee for Units, of which NIST is a member and which is one of 10 advisory committees of the International Committee for Weights and Measures (CIPM), submitted its proposal for a revised SI for consideration by the CIPM during its meeting in Paris, France, earlier this month. The CIPM, whose membership includes Willie May, director of NIST's Material Measurement Laboratory, modified and approved this proposal on Oct. 15, 2010. Based on this proposal, the CIPM will soon submit a resolution on a possible future revision of the SI for consideration at the next meeting of the General Conference on Weights and Measures (CGPM), the international diplomatic body that has the authority under the Meter Convention to adopt such a sweeping change. If the resolution passes and all the technical requirements it sets out are in place, a new SI could be adopted later in the decade.

* The seven SI base units from which all others are derived are the second (time), the meter (length), the kilogram (mass), the ampere (electric current), the kelvin (thermodynamic temperature), the mole (amount of substance) and the candela (luminous intensity).
** Current accepted value: 6.626 068 96(33) x 10-34 kg m2/ s
***The Boltzmann constant relates the change in the temperature of a system (such as a group of atoms and molecules) to the change in its thermal energy.

Edited on Nov. 2, 2010, for minor wording changes requested by BIPM.

Media Contact: Ben Stein, bstein@nist.gov, (301) 975-3097

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NIST, Harvard Researchers Share 2010 Julius Springer Prize for Applied Physics

NIST physical scientist Henri Lezec.

NIST physical scientist Henri Lezec (above), along with Federico Capasso of Harvard, won the 2010 Julius Springer Prize for Applied Physics. Henri Lezec is a project leader in NIST's Center for Nanoscale Science and Technology.

Credit: NIST
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National Institute of Standards and Technology (NIST) physical scientist Henri Lezec and Federico Capasso of Harvard have received the Julius Springer Prize for Applied Physics 2010 for their "pioneering achievements in nanoscale physics and applications." The Springer prize recognizes researchers who have made an outstanding and innovative contribution to the fields of applied physics and has been awarded annually since 1998.

Lezec received the award on Oct. 16, 2010, at the Julius Springer Forum on Applied Physics 2010, a special symposium in honor of the recipients held at Stanford University in Palo Alto, Calif. Attendees heard talks from both prize winners, as well as a series of special lectures given by luminaries in the field of nanoscale physics.

Lezec, who joined the NIST Center for Nanoscale Science and Technology in 2007, received his Ph.D. from MIT in 1992. He has held research positions at NEC Fundamental Research Laboratories, the Centre National de la Recherche Scientifique in France, and at the California Institute of Technology, and he worked in research, development and applications at Micrion Corporation.

Lezec's work spans a broad range of topics associated with the interaction of light with materials and nanoscale structures, i.e. plasmonics and nanoplasmonics. He is also known for pioneering the now widely applied use of the focused ion beam in fabricating nanoscale apertures and other structures.

Lezec's current work centers on the development of novel nanoscale measurement methods using materials that take advantage of the peculiar way that light behaves at the nanoscale. He has built and characterized structures that reverse the direction of refraction of light and created materials that seem to be attracted to and move toward light. For more information about Lezec's work and to view a selected list of his publications, see his bio at www.nist.gov/cnst/lezec.cfm

Media Contact: Mark Esser, mark.esser@nist.gov, 301-975-8735

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